Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895, which advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple.
It is often advantageous to build an end effector for the surgical stapler that is reusable. For instance, one patient may need a series of severing and stapling operations. Replacing an entire end effector for each operation tends to be economically inefficient. This is especially true if the end effector is built to be strong and reliable over repeated operations. To that end, staple cartridges are fitted into the end effector prior to each operation of the surgical stapler. Thus, a much smaller amount of the surgical staples is discarded after each use.
While the staple cartridge provides numerous advantages, it is desirable to prevent inadvertent firing of the surgical stapler when an unfired staple cartridge is not present. Otherwise, the severing of tissue may occur without the staples to minimize bleeding.
It is particularly desirable that preventing such inadvertent firing be accomplished in a reliable way that is not subject to an intervening malfunction. Moreover, for ease of manufacturing and assembly, it is further desirable that the lockout features be accomplished with a minimum number of components.
U.S. Pat. No. 5,129,570 by Schulze et al. discloses several lockout devices that prevent inadvertent firing when a cartridge is not present, and when the cartridge is spent or previously fired. Whereas the '570 devices do indeed lockout the device, the solutions were complex and required a number of extra components.
Consequently, a significant need exists for an improved surgical stapling and severing instrument that prevents inadvertent firing (i.e., severing and stapling) when a staple cartridge is not installed or is spent, having been previously fired.